1. Field of the Invention
The present invention relates generally to magnetic card readers and more particularly pertains to a slotless card reader wherein a magnetically encoded card is read through a magnetically permeable wall in a reader device.
2. State of the Prior Art
Magnetically encoded cards have come into widespread use in recent years for a variety of applications. One important use for such cards is in access control systems, such as are used to control parking lot gates, and generally to restrict operation of electrically actuated locks, doors and other devices.
Access control cards, also known as cardkeys, are laminar structures in which is incorporated magnetizable material such as barium ferrite, usually in sheet form on which magnetic patterns can be defined so as to encode information readable by a suitably constructed reader device. The manner of encoding and reading of such cards is well known.
Existing reader devices are housed in an enclosure which is provided with a slot for admitting the cards to be read.
Known card reader devices may be classified into two broad catagories, namely, static readers and dynamic readers. In a dynamic reader, the encoded card must be moved relative to the reader in order for the reading to take place. This is the case, e.g., in cards having an encoded magnetic stripe where the stripe must be moved past a read head which operates in a manner analogous to a playback head in an audio tape player.
A static reader by contrast reads the magnetically encoded card while the card is stationary relative to the reader. Typical of these are the tumbler operated readers commonly used in parking lot access gates in which mechanical tumblers are moved by magnetized areas or elements in the cards. The magnetic areas must be positioned so as to actuate the correct tumbler combination in the reader. In this type of reader, gravity is needed to return the tumblers to their normal position after the card is withdrawn. As a result, tumbler type readers have to be mounted vertically for proper operation. In addition to the tumbler mechanism for "reading" the information encoded on the card, this type of card reader is provided with a limit switch which is actuated by fully inserting a card into the slot. The switch completes the power circuit to the electrically operated access gate or lock if the proper combination of tumblers has been actuated. The slot in the reader housing thus serves to correctly position the card relative to the reader mechanism and to direct the card into contact with the limit switch by inserting the card into the reader through the slot.
In dynamic readers, the card slot serves a somewhat different purpose. A card transport mechanism is normally provided in the reader device which carries the card past a read head at a constant predetermined speed so as to avoid erroneous readings due to variations in card movement past the read-head. Constant speed would be difficult to achieve if the individual were allowed to manually move the card past the read-head. A further purpose served by the card slot is that by inserting the card into the reader, the individual forfeits control over the card. Thus, if the reader system determines that the card is being misused, the reader device may withhold the card and keep it out of reach of the person inserting it into the reader due to the restricted slot opening and where the reader device is built around electronic sensors which, unlike prior art mechanical tumbler readers, may be mounted at any desired angle away from the vertical without imparing the operation of the system.
Card slots in reader devices have been the target of malicious mischief and petty vandalism of the type where foreign matter, e.g., crumpled paper, chewing gum, and liquid beverages are introduced into the reader device through the card slot, jamming the reader and possibly damaging the mechanical or electronic components of the system. It is therefore desirable to provide a slotless card reader lacking any opening in the reader housing so as to avoid such vandalism, thereby increasing the reliability of the system and minimizing maintenance costs.
A slotless card reader is feasible in systems where some spacing is permissible between the card and the reader device to allow for a magnetically permeable wall member to be interposed therebetween. This is not usually the case with magnetic read heads used for reading data encoded on magnetic stripe in dynamic readers. These systems require close proximity between the strip and the read head in order to obtain adequate sensitivity and resolution of the encoded data. Such difficulties do not exist in access control cards where data is encoded in low density formats as in parking lot and similar relatively low security applications and particularly in readers using Hall effect devices. While Hall effect magnetic sensors and magnetic card readers using the same have been known and used commercially for some time in access control applications, heretofore no advantage has been taken of the characteristics of such readers which make practical the construction of slotless card readers.